The use of prefabricated insulating building and wall panels having metal front or back side surfaces or skins in building construction is well known. U.S. Pat. No. 5,181,353 to Herrington, Jr. discloses the assembly of conventional prefabricated building panels having a thermally insulating foam core sandwiched between two side sheet panels into a building structure. To assemble the building structure, tongued edge connectors are fitted into grooved panel edges which are devoid of the foam core, to join the edges of adjacent panels. A difficulty with the building panels shown in Herrington, Jr. exists, however, in that when the panel sides are formed from metal, no thermal break exists between the outer panel side, the connector and the inner panel side. The Herrington, Jr. panel system is therefore poorly suited for use in residential or commercial building applications as it permits heat loss by thermal conduction through the panel sides and connector.
One attempt to provide a structural panel which when assembled, provides a thermal break between the inner and outer panel side surfaces is disclosed in U.S. Pat. No. 5,373,678 to Hesser. Hesser teaches a panel having a foam core and metal side skins. Each panel edge includes a forwardly projecting metal tongue which is offset from the panel center towards one panel side, and a recessed metal groove spaced towards the opposing side. The groove is formed so as to be adapted to receive the forwardly projecting tongue of an abutting panel positioned edge to edge therewith. To provide a thermal break between the outer and inner sides of the panel, the tongue and groove of each edge are spaced from each other by an exposed angularly extending face of the foam core. The edge portion of the Hesser panel further includes a separate reinforcing member which is bent around the groove to provide the panel edge with enhanced rigidity. Assembly of a wall is achieved by positioning the panels in an edge-to-edge configuration and driving two separate rows of screws through each mated panel edge, wherein each row of screws is offset from the other.
The panel of Hesser suffers a disadvantage in that the addition of the reinforcing member to the panel construction complicates the panel manufacture, and increases the overall cost of the panel. As well, to manufacture the Hesser panel, the insulating foam core must be injected between the panels, and following curing, cut to the exposed angular face extending precisely from an innermost end of the tongue to an outermost edge of the edge groove. In cutting the injected foam along each edge of the panel, it is necessary that the foam face be formed at the exact angle so as not to interfere with the interlocking of the panel tongues into the grooves of the adjacent panel, when two panels are placed edge to edge. The process step of cutting the core after the foam injection between the panel sides further results in manufacturing inefficiencies, increasing the finished panel costs.
Because the tongue and groove of the Hesser panels are laterally offset from each other, to assemble each edge of the panels securely, it is essential that rows of screws be driven through the panels at least two laterally staggered locations. This increases both the cost and time involved in the panel erection. As well, because the screws used to secure each side portion of adjacent panels together may be laterally staggered along opposite sides of the panels, rotational forces on the panels may cause the panels to twist relative to each other between the rows of fasteners. The twisting in turn may disadvantageously result in the shearing of the tongues, or the delamination of the metal panel sides or skins from the insulating core.